A substrate processing apparatus such as a plasma processing apparatus employed in the production of, for instance, semiconductor devices includes a processing chamber where a substrate to be processed such as a semiconductor wafer or a liquid crystal substrate placed on a stage disposed therein undergoes an etching process, a film formation process or the like.
It is crucial to prevent contamination of the substrate being processed in such a substrate processing apparatus by particles (foreign matter taking the form of fine particles) of reaction products occurring while the substrate is being processed in the processing chamber or fine particles entering the processing chamber from the outside.
For instance, if the wafer stage disposed inside the processing chamber becomes contaminated by particles, particles may settle onto the rear surface of the substrate placed on the stage, which may result in the contamination spreading through the subsequent processes. In addition, if the inner wall of the processing chamber is contaminated by particles, some particles on the inner wall may settle onto the next substrate to undergo the processing, and in this case, the processing may be adversely affected. The contamination of substrates undergoing processing with particles, which occurs as described above, leads to problems including a reduced yield of semiconductor devices manufactured on the substrates as final products.
The methods proposed in the related art to be adopted to effectively eliminate particles in the processing chamber include a cleaning method whereby the particles are lifted off and scattered and eliminated with maxwell stress generated by, for instance, applying a high voltage to the stage (see Japanese Laid Open Patent Publication No. 2005-101539). More specifically, as the processing chamber is evacuated while supplying an inert gas into the processing chamber, a two-stage cleaning process is executed by first applying a high-voltage to the stage in a low-pressure environment and then applying a high voltage to the stage in a high-pressure environment, thereby effectively lifting off and scattering the particles and then discharging them from the processing chamber.
The processing chamber normally assumes a specific structure designed in correspondence to the type of wafer processing to be executed in the processing chamber, the processing conditions (e.g., the processing chamber internal pressure, the processing gas type, the levels of high-frequency power applied to the electrodes and the level of voltage applied to the stage) and the parts disposed within the processing chamber. It has been learned that by actually cleaning processing chambers assuming various structures, an abnormal electrical discharge (e.g., an arc discharge) sometimes occurs while a voltage is applied to the stage in the low-pressure environment depending upon the structure adopted in the particular processing chamber. Such an abnormal electrical discharge may cause an emergency stop of the entire substrate processing apparatus, which, in turn, may lead to reduced throughput for the overall substrate processing apparatus or damage to a component such as the stage.